The role of BH3-mimetic drugs in the treatment of pediatric hepatoblastoma

Celecoxib Analogues for Cancer Treatment: An Update on OSU-03012 and 2,5-Dimethyl-Celecoxib

Cyclooxygenase-2 (COX-2) is an important enzyme involved in prostaglandins biosynthesis from arachidonic acid. COX-2 is frequently overexpressed in human cancers and plays a major tumor promoting function. Accordingly, many efforts have been devoted to efficiently target the catalytic site of this enzyme in cancer cells, by using COX-2 specific inhibitors such as celecoxib. However, despite their potent anti-tumor properties, the myriad of detrimental effects associated to the chronic inhibition of COX-2 in healthy tissues, has considerably limited their use in clinic. In addition, increasing evidence indicate that these anti-cancerous properties are not strictly dependent on the inhibition of the catalytic site. These findings have led to the development of non-active COX-2 inhibitors analogues aiming at preserving the antitumor effects of COX-2 inhibitors without their side effects. Among them, two celecoxib derivatives, 2,5-Dimethyl-Celecoxib and OSU-03012, have been developed and suggested for the treatment of viral (e.g., recently SARS-CoV-2), inflammatory, metabolic diseases and cancers. These molecules display stronger anti-tumor properties than celecoxib and thus may represent promising anti-cancer molecules. In this review, we discuss the impact of these two analogues on cancerous processes but also their potential for cancer treatment alone or in combination with existing approaches.

Knockdown of NRAGE Impairs Homologous Recombination Repair and Sensitizes Hepatoblastoma Cells to Ionizing Radiation

Background: NRAGE (neurotrophin receptor-interacting melanoma antigen-encoding gene homolog) has a complex role and regulates cell growth in different tumor cells. Although NRAGE was been discovered for more than 10 years ago, the function of NRAGE in hepatoblastoma (HB) cells is currently unknown. Materials and Methods: The expression of NRAGE was detected by reverse transcription-quantitative polymerase chain reaction assay or western blotting assay. Cellular apoptosis was analyzed to estimate the effect of NRAGE under radiation. The ability of clonogenic capacity was evaluated to confirm the influence of proliferation for NRAGE by radiation. The immunofluorescence assay was used to further study the expression of NRAGE under radiation. A nude mouse tumor xenograft model was constructed to confirm the effect of NRAGE deficiency under radiation conditions in vivo. Results: The authors determined that deletion of NRAGE significantly inhibited HB cell proliferation in vitro and in vivo, and NRAGE knockdown apparently sensitized HB cells to ionizing radiation (IR). Further mechanistic studies revealed that NRAGE plays a critical role in homologous recombination by inhibiting the expression of RNF8 (ring finger protein 8) and BARD1 (BRCA1 associated RING domain 1) and the recruitment of RAD51. Conclusions: The authors demonstrated that downregulation of NRAGE sensitizes HB cell lines to IR in vitro and in vivo. It provides a promising therapeutic strategy for HB patients by specifically targeting NRAGE.

Ginsenoside Rg1 impairs homologous recombination repair by targeting CtBP-interacting protein and sensitizes hepatoblastoma cells to DNA damage

The ginsenoside Rg1, the primary pharmacologically active ingredient of the traditional Chinese herb ginseng, is widely used in the clinical treatment of diseases of the immune and nervous systems. Recent studies have shown that it also has an antitumor effect. In this study, we explored the effects of Rg1 on hepatoblastoma (HB) and its underlying mechanisms. We demonstrated that Rg1 significantly inhibited HB cell growth both in vivo and in vitro. Mechanistic studies revealed that Rg1 impaired homologous recombination and triggered double-strand breaks in HB cells by directly targeting CtBP-interacting protein (CtIP), a key double-strand break repair factor, which is highly expressed in HB tissues. Moreover, we also demonstrated that Rg1 sensitized HB cells to DNA-damaging agents both in vitro and in vivo. In conclusion, our data not only demonstrate the potential clinical application of Rg1 as a novel chemotherapeutic candidate but also offer a mechanism-based therapeutic option by which DNA-damaging agents can be used in combination with Rg1 to target HB.

Sonoporation by microbubbles as gene therapy approach against liver cancer

INTRODUCTION

An innovative method, known as sonoporation, was used to induce the expression of silenced genes, such as (but not restricted to) TRAIL and p53, in liver cancer cells (HepG2). The principal aim of the present study was the re-activation of silenced apoptotic pathways in liver cancer models, by using diagnostic synovial microbubble as plasmid gene delivery tools in combination with epigenetic treatments.

MATERIAL AND METHODS

HepG2 cells were used as a liver cancer model. Microbubbles (Sonovue®) were chosen as gene deliver system in combination with the sonoporation approach. Plasmid pEGFP-TRAIL and pEGFP-p53 were selected and propagated in Escherichia coli grown in LB broth, in order to obtain the necessary amount.

RESULTS

Sonoporation was induced by using transducer (Sonitron 2000) and, among the several conditions tested, 3 MHz, 51% Duty Cycle, and 5 W/cm2, 30 s resulted as the best parameters. Data collected showed a dose dependent effect in terms of output energy. A transfection efficacy of 30 - 50% was achieved and recombinant gene expression induced apoptotic effects. In order to increase efficacy, we used the histone deacetylase inhibitor (HDACi, entinostat) MS-275, able to activate TRAIL and thus inducing a stronger pro-apoptotic effect in combination with TRAIL-gene re-expression.

CONCLUSION

For the first time, it was shown the possibility to induce the exogenous expression of the pro-apoptotic gene TRAIL and p53 in a liver cancer HepG2 cells via a sonoporation procedure. The epigenetic treatment using HDACi was able to increase the pro-apoptotic effects of the gene therapy.

Co-delivery of cisplatin and CJM-126 via photothermal conversion nanoparticles for enhanced synergistic antitumor efficacy

Polymeric biomaterials that can be smartly disassembled through the cleavage of the covalent bonds in a controllable way upon an environmental stimulus such as pH change, redox, special enzymes, temperature, or ultrasound, as well as light irradiation, but are otherwise stable under normal physiological conditions have attracted great attention in recent decades. The 2-(4-aminophenyl) benzothiazole molecule (CJM-126), as one of the benzothiazole derivatives, has exhibited a synergistic effect with cisplatin (CDDP) and restrains the bioactivities of a series of human breast cancer cell lines. In our study, novel NIR-responsive targeted binary-drug-loaded nanoparticles encapsulating indocyanine green (ICG) dye were prepared as a new co-delivery and combined therapeutic vehicle. The prepared drug-loaded polymeric nanoparticles (TNPs/CDDP-ICG) are stable under normal physiological conditions, while burst drugs release upon NIR laser irradiation in a mild acidic environment. The results further confirmed that the designed co-delivery platform showed higher cytotoxicity than the single free CDDP due to the synergistic treatment of CJM-126 and CDDP in vitro. Taken together, the work might provide a promising approach for effective site-specific antitumor therapy.

Hepatoblastoma with pure fetal epithelial differentiation in a 10-year-old boy: A rare case report and review of the literature

RATIONALE

Hepatoblastoma is a rare malignant embryonal tumor that only accounts for approximately 1% of all pediatric cancers and mostly develops in children younger than 5 years old. Moreover, the occurrence of hepatoblastoma in adults is extremely rare.

PATIENT CONCERNS

Herein, we present a rare case of hepatoblastoma with pure epithelial differentiation in a 10-year-old boy.Pathological examination was performed. The tumor was 15 cm × 15 cm in size with clear margins. The cut surface was multiple nodular and grey-yellow. Histologically, the small cuboidal tumor cells were arranged in trabeculae with 2-3 cell layers. The tumor cells had eosinophilic or clear cytoplasm, formed dark and light areas, and were positive for alpha-fetoprotein, CK, CK8/18, CD10, hepatocyte, and GPC3. CD34 staining revealed that the sinusoids were lined by endothelial cells in the tumor tissues. The Ki67 index was approximately 20%.

DIAGNOSES

Based on these findings, the case was diagnosed as hepatoblastoma with pure fetal epithelial differentiation.

INTERVENTIONS

The tumor was completely removed.

OUTCOMES

No recurrence was found 3 months after the operation.

LESSONS

Hepatoblastoma with pure epithelial differentiation can also occur in older children. Children rarely notice and report any physical abnormality, and this may be among the primary reasons for the late diagnosis of the tumor. Annual heath checks may be beneficial in the detection of these rare tumors and improvement of patient outcomes.

Downregulation of transcription factor GATA4 sensitizes human hepatoblastoma cells to doxorubicin-induced apoptosis

Hepatoblastoma, the most common type of pediatric liver cancer, is treated with a combination of surgery and chemotherapy. An essential drug in the treatment of hepatoblastoma is doxorubicin, which in high doses is cardiotoxic. This adverse effect is due to downregulation of cardiac expression of transcription factor GATA4, leading in turn to diminished levels of anti-apoptotic BCL2 (B-cell lymphoma 2) protein family members. GATA4 is also expressed in early fetal liver, but absent from normal postnatal hepatocytes. However, GATA4 is highly expressed in hepatoblastoma tissue. In this study, we assessed the role of GATA4 in doxorubicin-induced apoptosis of hepatoblastoma cells. Herein, we demonstrate that doxorubicin decreases GATA4 expression and alters the expression pattern of BCL2 family members, most profoundly that of BCL2 and BAK, in the HUH6 hepatoblastoma cell line. Silencing of GATA4 by siRNA prior to doxorubicin treatment sensitizes HUH6 cells to the apoptotic effect of this drug by further shifting the balance of BCL2 family members to the pro-apoptotic direction. Specifically, expression levels of anti-apoptotic BCL2 were decreased and pro-apoptotic BID were increased after GATA4 silencing. On the whole, our results indicate that since high endogenous levels of transcription factor GATA4 likely protect hepatoblastoma cells from doxorubicin-induced apoptosis, these cells can be rendered more sensitive to the drug by downregulation of GATA4.

Obatoclax, a Pan-BCL-2 Inhibitor, Targets Cyclin D1 for Degradation to Induce Antiproliferation in Human Colorectal Carcinoma Cells

Colorectal cancer is the third most common cancer worldwide. Aberrant overexpression of antiapoptotic BCL-2 (B-cell lymphoma 2) family proteins is closely linked to tumorigenesis and poor prognosis in colorectal cancer. Obatoclax is an inhibitor targeting all antiapoptotic BCL-2 proteins. A previous study has described the antiproliferative action of obatoclax in one human colorectal cancer cell line without elucidating the underlying mechanisms. We herein reported that, in a panel of human colorectal cancer cell lines, obatoclax inhibits cell proliferation, suppresses clonogenicity, and induces G₁-phase cell cycle arrest, along with cyclin D1 downregulation. Notably, ectopic cyclin D1 overexpression abrogated clonogenicity suppression but also G₁-phase arrest elicited by obatoclax. Mechanistically, pre-treatment with the proteasome inhibitor MG-132 restored cyclin D1 levels in all obatoclax-treated cell lines. Cycloheximide chase analyses further revealed an evident reduction in the half-life of cyclin D1 protein by obatoclax, confirming that obatoclax downregulates cyclin D1 through induction of cyclin D1 proteasomal degradation. Lastly, threonine 286 phosphorylation of cyclin D1, which is essential for initiating cyclin D1 proteasomal degradation, was induced by obatoclax in one cell line but not others. Collectively, we reveal a novel anticancer mechanism of obatoclax by validating that obatoclax targets cyclin D1 for proteasomal degradation to downregulate cyclin D1 for inducing antiproliferation.

Antagonism of Bcl-XL is necessary for synergy between carboplatin and BH3 mimetics in ovarian cancer cells

BACKGROUND

BH3 mimetics are a class of drugs that antagonize the Bcl-2 family of apoptosis inhibitors. We have previously shown that these compounds can potentiate the activity of carboplatin against several ovarian cancer cell lines. However, recent clinical studies have highlighted that BH3 mimetics which antagonise Bcl-XL are associated with significant thrombocytopenia. This has led to the development of ABT-199 which specifically inhibits Bcl-2. Unfortunately, Bcl-XL appears to be more frequently deregulated in ovarian cancer than Bcl-2. We therefore compared the ability of ABT-199, and the Bcl-XL selective compound WEHI-539, to potentiate the activity of carboplatin in ovarian cancer cell lines.

METHODS

WEHI-539, ABT-737 and ABT-199 were tested in combination with carboplatin using a panel of 6 ovarian cancer cell lines. The activity of the drugs was evaluated using cell growth assays, staining with trypan bue and measurement of apoptosis by measuring caspase 3/7 activity, PARP cleavage and annexin-V/propidium iodide staining.

RESULTS

We found that WEHI-539 and ABT-737, but not ABT-199, were synergistic with carboplatin in cell growth assays and potentiated cell death when assessed by trypan blue staining. Furthermore, WEHI-539 and ABT-737 augmented carboplatin induced caspase 3/7 activity, PARP cleavage and annexin V labelling, but ABT-199 failed to do so.

CONCLUSIONS

These observations suggest that compounds which target Bcl-XL are necessary if BH3 mimetics are to be successfully used to treat patients with ovarian cancer and this highlights the need to develop strategies to minimize thrombocytopenia induced by such compounds.

Antagonism of Bcl-XL is necessary for synergy between carboplatin and BH3 mimetics in ovarian cancer cells

Background

BH3 mimetics are a class of drugs that antagonize the Bcl-2 family of apoptosis inhibitors. We have previously shown that these compounds can potentiate the activity of carboplatin against several ovarian cancer cell lines. However, recent clinical studies have highlighted that BH3 mimetics which antagonise Bcl-X_L are associated with significant thrombocytopenia. This has led to the development of ABT-199 which specifically inhibits Bcl-2. Unfortunately, Bcl-X_L appears to be more frequently deregulated in ovarian cancer than Bcl-2. We therefore compared the ability of ABT-199, and the Bcl-X_L selective compound WEHI-539, to potentiate the activity of carboplatin in ovarian cancer cell lines.

Methods

WEHI-539, ABT-737 and ABT-199 were tested in combination with carboplatin using a panel of 6 ovarian cancer cell lines. The activity of the drugs was evaluated using cell growth assays, staining with trypan bue and measurement of apoptosis by measuring caspase 3/7 activity, PARP cleavage and annexin-V/propidium iodide staining.

Results

We found that WEHI-539 and ABT-737, but not ABT-199, were synergistic with carboplatin in cell growth assays and potentiated cell death when assessed by trypan blue staining. Furthermore, WEHI-539 and ABT-737 augmented carboplatin induced caspase 3/7 activity, PARP cleavage and annexin V labelling, but ABT-199 failed to do so.

Conclusions

These observations suggest that compounds which target Bcl-X_L are necessary if BH3 mimetics are to be successfully used to treat patients with ovarian cancer and this highlights the need to develop strategies to minimize thrombocytopenia induced by such compounds.